1. Field of Invention
The invention relates to a light-emitting diode (LED) package. More particularly, the invention relates to a white LED package containing plural blue LED chips emitting light from both front and rear surfaces thereof.
2. Description of Related Art
A light-emitting diodes (LED) package is completed by die bonding, wire bonding, molding, and pinning to weld LED chips to a printed circuit board. The white LED package is usually a LED package includes a blue LED chip covered by yellow fluorescent glue to form white extracting light The white LED package can be applied to various products, such as lamps, a backlight module of a liquid crystal display, and the like.
A white LED package can be divided into a package containing a single blue LED chip or a package containing plural blue LED chips connected serially or in parallel. For products like lamps and lanterns, the difference between using a white LED package containing plural blue LED chips and using plural white LED packages respectively containing a single LED chip is that the former one has a simpler structure and does not require repeating welding process to respectively each single LED package.
For the above-described white LED packages, in order to improve the light extraction efficiency thereof, a light reflecting surface is disposed under a bonded blue LED chip to reflect the lateral light and the rear light of the blue LED chip to increase the brightness of the extracted light.
FIG. 1 illustrates a conventional white LED package 100 containing a single LED chip. The white LED package 100 has a light reflection cup 110, and the inner surface 111 of the light reflection cup 110 is white. Blue LED chip 120 is bonded on a negative electrode plate 131, and electrically connected to the negative electrode plate 131 and a positive electrode plate 132. Silver coatings (not shown) are disposed on the surfaces of the negative electrode plate 131 and the positive electrode plate 132. The design of these silver coatings and the white inner surface 111 of the light reflection cup 110 is used for reflecting the light emitted from the lateral and rear directions of the blue LED chip 120 as much as possible and thus increase the brightness of the extracting white lights.
FIG. 2 illustrates a conventional white LED package 200 containing plural LED chips. The white LED package 200 has a circuit board 210 having a ground serving as a light reflection area 211. Plural blue LED chips 220 are bonded on the light reflection area 211, and a yellow fluorescent glue layer 212 covers the plural blue LED chips 220. This design is used to reflect light emitted from the lateral and the rear directions of the plural blue LED chips 220 as much as possible and thus increase the brightness of the extracting lights.
The above-described conventional LED packages both provide only one light reflection surface, and the emitted light can only be extracted from the single front surface. Therefore, the emitted light cannot be extracted from both of the front surface and the rear surface.